Nasa scientists have announced that the space agency plans to launch another mega-rover to Mars after the success of Curiosity.

The space agency said the spacecraft will be built from spare parts left over from the one-tonne Curiosity rover. It would also use the novel landing system that delivered the car-size rover to Mars earlier this year.

The new mission is scheduled for 2020 and is estimated to cost about US$1.5 billion. Nasa said the new mission was another step toward eventually sending astronauts to the red planet in the 2030s.

In the coming months, a team of experts will debate whether the new rover should have the ability to drill into rocks and store pieces for a future pickup - either by another spacecraft or humans.

NASA plans to set up a team of scientists to refine plans for the rover and issue a solicitation next summer.

The National Academy of Sciences last year ranked a Mars sample return mission as its top priority in planetary science for the next decade.

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"The (science) community already has come forward with a very clear message about what the content of the next Mars surface mission should be, and that is to cache the samples that will come back to Earth," said Steve Squyres with Cornell University.

"That's really a necessary part of having this mission," he said.

Curiosity landed on Mars on Aug 6. It is looking for signs that the planet supported life in the distant past. It is expected to still be working when the new rover arrives in eight years' time.

The administration of President Barack Obama "is committed to a robust Mars exploration program," Nasa Administrator Charles Bolden said in a statement.

"With this next mission, we're ensuring America remains the world leader in the exploration of the Red Planet, while taking another significant step toward sending humans there in the 2030s."